const defaultState = {
    inputValue:"hello",
    list :[1, 2]
}
// reducer 可以接受state， 但是绝对不能修改state
export default (state = defaultState, action) =>{
    if (action.type === 'change_input_value') {
        const newState = JSON.parse(JSON.stringify(state))
        newState.inputValue = action.value
        return newState
    }
    if (action.type === 'add_todo_item') {
        const newState = JSON.parse(JSON.stringify(state))
        newState.list.push(newState.inputValue)
        newState.inputValue = ''
        return newState
    }
    if (action.type === 'delete_todo_item') {
        const newState = JSON.parse(JSON.stringify(state))
        newState.list.splice(action.index, 1)
        return newState
    }
    return state
}